1. Field of the Invention
The present invention relates generally to the fields of cellular biology and diagnosis of neoplastic disease. More specifically, the present invention relates to a transmembrane serine protease termed Tumor Associated Differentially-Expressed Gene-12 (TADG-12), which is overexpressed in ovarian carcinoma.
2. Description of the Related Art
Tumor cells rely on the expression of a concert of proteases to be released from their primary sites and move to distant sites to inflict lethality. This metastatic nature is the result of an aberrant expression pattern of proteases by tumor cells and also by stromal cells surrounding the tumors (1-3). For most tumors to become metastatic, they must degrade their surrounding extracellular matrix components, degrade basement membranes to gain access to the bloodstream or lymph system, and repeat this process in reverse fashion to settle in a secondary host site (3-6). All of these processes rely upon what now appears to be a synchronized protease cascade. In addition, tumor cells use the power of proteases to activate growth and angiogenic factors that allow the tumor to grow progressively (1). Therefore, much research has been aimed at the identification of tumor-associated proteases and the inhibition of these enzymes for therapeutic means. More importantly, the secreted nature and/or high level expression of many of these proteases allows for their detection at aberrant levels in patient serum, e.g. the prostate-specific antigen (PSA), which allows for early diagnosis of prostate cancer (7).
Proteases have been associated directly with tumor growth, shedding of tumor cells and invasion of target organs. Individual classes of proteases are involved in, but not limited to 1) the digestion of stroma surrounding the initial tumor area, 2) the digestion of the cellular adhesion molecules to allow dissociation of tumor cells; and 3) the invasion of the basement membrane for metastatic growth and the activation of both tumor growth factors and angiogenic factors.
For many forms of cancer, diagnosis and treatment has improved dramatically in the last 10 years. However, the five year survival rate for ovarian cancer remains below 50% due in large part to the vague symptoms which allow for progression of the disease to an advanced stage prior to diagnosis (8). Although the exploitation of the CA125 antigen has been useful as a marker for monitoring recurrence of ovarian cancer, it has not proven to be an ideal marker for early diagnosis. Therefore, new markers that may be secreted or released from cells and which are highly expressed by ovarian tumors could provide a useful tool for the early diagnosis and for therapeutic intervention in patients with ovarian carcinoma.
The prior art is deficient in the lack of the complete identification of the proteases overexpressed in carcinoma, therefore, deficient in the lack of a tumor marker useful as an indicator of early disease, particularly for ovarian cancers. Specifically, TADG-12, a transmembrane serine protease, has not been previously identified in either nucleic acid or protein form. The present invention fulfills this long-standing need and desire in the art.